1. Field of the Invention
This invention relates to a conveyor means for conveying wafers one by one.
2. Prior Art
As a means of conveying thin sheet-like goods such as semiconductor wafers in a clean room, there are available (1) the method of floating wafers by air pressure and then conveying them by injection air pressure, (2) the method of conveying wafers placed on a conveyor and the like.
However, in the case of the former method (1), it requires a device for supplying air pressure at all times and also involves a drawback that dust is liable to rise from a guide or a stopping device along the transporting path. Thus, this method is not suitable for use in a clean room.
In the case of the latter method (2), when wafers are being conveyed on a belt, dust from the belt sticks to the backs of the wafers and as a result, the yield of the wafer manufacturing process is reduced.
Conventionally, between processing machines wafers were usually transported in a wafer cassette which can hold several wafers, instead of transporting wafers one by one. However, with the increasing diameter of the wafers and with the growing tendency to multi-variety small-lot production of the wafers in recent years, means for conveying wafers one by one has come to be demanded. Moreover, processing of waferS has become more and more minute and this tendency necessitates a conveyor means with a higher degree of cleanness.